Production of unsaturated hydrocarbons from liquid hydrocarbons



p 1962 A. STEINHOFER' ETAL 3,054,839

PRODUCTION OF UNSATURATED HYDROCARBONS FROM LIQUID HYDROCARBONSFiledApril Is. 1959 2 Sheets-Sheet .1 L- I g: 1

DIAMETER OF THE. REACTION CHAMBER MEASUREMENT POINTY MEASUREMENT PO\NT132:

MEASUREMENT PomT m 35o" MEASUREMENT POHNT IE MEASUREMENT pom-r z:

INVENTORS: ADOLF STE\NHOF ER KARL BU$CHMANN 150' LED UNTERSTENEOIEFER p,@61

P 1962 A. STEINHOFER ETAL 3,054,839

PRODUCTION OF UNSATURATED HYDROCARBONS FROM LIQUID HYDROCARBONS 2Sheets-Sheet 2 Filed April 13. 1959 United States Patent Ofifice3,054,839 Patented Sept. 18, 1962 3,054,839 PRODUCTION OF UNSATURATEDHYDROCAR- BONS FROM LIQUID HYDROCARBONS Adolf Steinhofer, Ludwigshafen(Rhine), Karl Buschmann, Neustadt an der Weinstrasse, and LeoUnterstenhoefer, Limhurgerhof (Pfalz), Germany, assignors to BadiseheAnilindz Soda-Fahrik Aktiengesellschaft, Ludwigshafen (Rhine), GermanyFiled Apr. 13, 1959, Ser. No. 805,804 Claims priority, applicationGermany Apr. 12, 1958 5 Claims. (Cl. 260-683) This invention relates tothe production of unsaturated hydrocarbons from liquid hydrocarbons.More specifically, the present invention is directed to the productionof unsaturated hydrocarbons from low and high boiling liquidhydrocarbons while avoiding the formation of carbon black and coke.

It is known to prepare unsaturated hydrocarbons by partial combustion ofhydrocarbons, if desired with the supply of steam. The initial materialsare introduced into the reaction chamber in the form of vapor or in afinely atomized state, for example through jets. The heat necessary forthe cracking is produced either by burning part of the initial materialor other combustible substances in the reaction chamber or in a specialchamber in front of the same.

It is also known to produce fuel gases by burning hydrocarbons with airor oxygen in a cylindrical combustion chamber, a ring of flame adjacentthe wall being produced by tangential introducion of the two reactantsat appropriate high speeds. Into this ring, the atomized liquidhydrocarbon is then sprayed axially with the addi tion of steam. Anintensive thorough mixing of the components thereby takes place and thedesired cracking reaction occurs.

This method has the disadvantage that, by reason of the sudden mixing ofthe components, cracking of part of the substances to be cracked maytake place at the hot wall of the reaction chamber as a consequence ofwhich carbon black and coke form and may cause diffrculties bydeposition and stoppage both in the reaction chamber and in the attachedapparatus. Moreover, the yield of unsaturated hydrocarbons is diminishedby the said formation of carbon black and coke. This disadvantage isespecially evident when high boiling hydrocarbons, for example bunker Coils, serve as initial material, because on the one hand these aredifficult to atomize and on the other hand they tend in a high degree toform carbon black and coke.

We have now found that the said disadvantages are avoided by introducingthe liquid hydrocarbons to be cracked through a tube with a free outletinto the reaction chamber in the neighborhood of the inner wall, andintroducing oxygen or oxygen-containing gas, and if desired alsosuperheated steam, combustion gas and/or return gas, tangentially athigh speed through a slit near to the said point of introduction. By thespeed of the said gas, and owing to the fact that the first part of thereaction chamber, into which the hydrocarbons and the said gas enter, isconically constricted at the end, detachment of the vortex from the wallis avoided. The liquid hydrocarbon is vaporized and partially burnt, andthe reaction of the vapors formed is initiated. The further reaction ofthe initial materials takes place in a second part of the reactionvessel which is cylindrical or advantageously widens like a diffuser andthen preferably proceeds cylindrically.

By working in this way, the sudden mixing of the hydrocarbons andoxygen-containing gas, which takes place in the known method and leadsto the said disturbances by coke formation, is avoided. The speed whichis necessary in order to avoid detachment of the vortex ofoxygen-containing gas from the inner Wall in the first part of thereaction chamber and consequent undesirable rapid mixing with thehydrocarbons may readily be ascertained empirically. The effect ofdifferent speeds is clearly shown at temperature measurement pointsdistributed over the length and cross-section of the reaction vessel. Itmay also be observed by determination of the oxygen content in gassamples withdrawn from different places, as well as by the coke depositswhich show clearly at gas speeds which are too slow.

The gas speed of the oxygen-containing gas is always greater than thatof the hydrocarbons, preferably more than meters per second,advantageously to 200' meters per second higher than that of thehydrocarbons. There then forms in the neighborhood of the axis of thereaction vessel a region of reduced pressure into which the bulk of thevaporized hydrocarbon is drawn.

The liquid initial material may flow in, like the oxygen-containing gas,tangentially, but it may also be introduced radially or parallel to theaxis in the neighborhood of the inner wall of the reaction vessel. Theprocess has the advantage that it is also possible to work uphydrocarbon mixtures of any type, for example light naphtha ordistillation residues with a viscosity of 760 centistoke at 100 C.without the formation of coke and carbon black. Since an apparatus forvaporization and atomization is not required, there is thus opened up anew way of cracking high boiling oil residues which are difiicult tovaporize or atomize.

The course of the cracking is as follows:

The high speed oxygen-containing gas, if desired mixed with steam,spreads out the liquid hydrocarbon mixture to be cracked as a film-likeband on the wall of the chamber and evaporation takes place from thisband. The mixture of steam and oxygen rotating along the cylindricalwall produces an axial region of reduced pressure into which thevaporous hydrocarbon is drawn. Along the path through the reactionchamber, thanks to the said constructive features, there takes placewith decreasing spin the mixing of oxygen, and possibly steam, with thehydrocarbon so that a progressive partial combustion takes place. Thetemperature of the reaction mixture accordingly increases on its waythrough the reaction chamber and does not reach the desired finalcracking temperature until the end of the reaction chamber.

FIGURE 1 of the accompanying drawings reproduces the course of thetemperature in the reaction chamber. This course in the reaction chamberis readily detectable analytically. In the first third of the reactionchamber there occurs in the zones near the Wall mainly oxygen at lowinitial temperatures. These temperatures slowly rise as the distancefrom the point of introduction of the gases into the reaction chamberincreases, corresponding to the decreasing supply of oxygen. On theother hand, unchanged hydrocarbon is still detectable in the interior.In the mixing zone, in which by reason of the continually declining spinthere take place the mixing and reaction of the outer rotating layer ofsteam and oxygen with the hydrocarbon near to the axis, carbon monoxide,hydrogen, olefins and methane are detectable. In the last quarter of thereaction chamber there is found the uniform final composition of thecracking gas in the zone of uniform temperature. This course alsoexplains why no formation of coke takes place on the walls of thechamber. The hydrocarbons react gradually from the interior outward withthe mixture of oxygen and steam which is rapidly rotating along thewall, with continually increasing temperature, so that it is quiteimpossible for uncracked, readily crackable hydrocarbon vapors to passthrough to the hot wall and lead to coke deposition thereon. At the endof the reaction cham- 3 her the cracked gas is quenched in known mannerWith water.

An embodiment of the process according to this invention will'now bedescribed by way of example with reference to FIGURE 2 of theaccompanying drawings. Into part 1 of a cylindrical reaction vesselwhich has a conical constriction at its end, a mixture of oxygen andsteam is introduced through a slot 3 at a speed of 100 to 200 meters persecond from tubes 4 and 5 and a channel 6. Through a tiltable supplypipe 7 which is fixed or capable of adjustment in height and which has afree outlet there flows under a slight excess pressure of 500 to 1000mm. Water column a petroleum fraction of the middle boiling range intothe channel 6 and thence into the reaction chamber 1 where it is spreadout into a film on the inner Wall of the reaction vessel by the kineticenergy of the gaseous or vaporous substance. The oil is vaporized at thewall of the reaction vessel which has been preheated by combustion gasesintroduced at 9. While a part of the oil vapor is burnt to cover theheat required for cracking, the bulk of the oil vapor passes into theneighborhood of the axis of the reaction vessel.

In order to prevent a sudden intensive mixing of the reactants in part 2of the reaction vessel, the transition frompart 1 to part2 takes placethrough a conical intermediate member 10 having such a cone angle that adiminution in the rotational speed of the rotating gas and vapor occursto the desired extent without a troublesome eddying of the wholemixture. The cone angle preferably does not exceed 10.

The .part 2 of the reaction chamber is made cylindrical. It may,however, be continued wholly or partly conically. The reaction isdiscontinued in known manner by spraying in cooling water at 11 in orderto prevent decomposition of the product.

Part 1 of the reaction chamber is lined with heatresistant material. Itis preferable to arrange on its circumference channels for preheatingthe oxygencontaining gas. The remainder of the reaction vessel may alsobe wholly or partly lined with heat-resistant material.

The speed ofthe gas and vapor introduced into the channel "6 maybe'adjusted as desired depending on the initial material to be crackedby interchangeable inserts with varying cross sections. It is possibleto observe the film formation, ignition and so on through a door 12 atone end of the reaction vessel.

The process is carried out at atmospheric or slightly increasedpressure, for example at 2 excess atmospheres; higher pressures may beused, however, and in this case the hydrogenating action of the hydrogenformed in the reaction chamber is promoted. To increase this action,hydrogen or hydrogen-containing gases may also be incorporated.

The cooling of the cracked gas formed is eifected in known manner bywater, but may also be ettected by decompressing the gas in a nozzle orwith the utilization of energy.

FIGURE 3 is a cross-sectional view 'of the apparatus shown in FIGURE 2taken along a line through points A-A The following example will furtherillustrate thisinvention 'but the invention is not restricted to thisexample.

Example 95 kilogramsper hour of a light gasoline with a boiling range upto 105 C. is allowed to flow into a reaction vessel according to FIGURE2 which has a total length of 2400 mm. and which has in theunconstricted part a diameter of 350mm. At the same time there aresupplied to the reaction vessel per kilogram of light gasoline, 0.282Nm; of oxygen and 0.525 kilogram of steam. The cracking ternperature is725 C. at the end of the reaction chamber. The cracked gas leaving thereaction chamber is cooled with Water. It has the following compositionin percent by volume:

of CO2 10.6 of C H and higher unsaturated hydrocarbons 0.5 of C H OfC2H4 of H2 33.4 of CO 5.0 of C H and higher hydrocarbons 17.6 of CH;

Traces of O and N The upper calorific value is 9580 kcals. The totalyield of olefins amounts to 0.42 kilogram per kilogram of light gasolineintroduced.

We claim:

1. A process for the production of unsaturated hydrocarbons from liquidhydrocarbons which comprises introducing a liquid hydrocarbon through aconduit having a free outlet into a cylindrical reaction vessel in theneighborhood of the inner wall of said vessel; introducing a gasselected from the group consisting of oxygen and oxygen-containing gasestangentially into said vessel through a slot near the point ofintroduction of said liquid hydrocarbon and at a speed greater than thespeed of said liquid hydrocarbon, whereby said hydrocarbon forms a'fihnlike band of liquid on said wall; rotating said gas along the wallof said vessel at a sufiicient speed to prevent a detachment of thevortex from the wall, said rotating gas forming an axial region ofreduced pressure in said vessel into which said hydrocarbon in vaporousform is drawn; passing said rotating gas through a conical member havinga cone angle of less than 10, the rotational speed of said gasdecreasing as it passes through said conical member, whereby progressivepartial combustion of said hydrocarbon takes place; and passing saidrotating gas and said vaporous hydrocarbon into a second cylindricalmember which is adjacent to said conical member, wherein the reaction iscompleted.

2. A process for the production of unsaturated hydrocarbons .from liquidhydrocarbons which comprises introducing a liquidhydrocarbon through aconduit having a free outlet into a cylindrical reaction vessel in theneighborhood of the inner wall of said vessel; introducing a gasselected from the group consisting of oxygen and oxygen-containing gasestangentially into the first zone of said vessel through a slot near thepoint of introduction of said liquid hydrocarbon and at a speed greaterthan the speed of said liquid hydrocarbon, whereby said hydrocarbonforms a filmlike band of liquid on said wall; rotating said gas alongthe wall of said vessel at a sufiicient speed to prevent a detachment ofthe vortex from the Wall, said rotating gas forming an axial region ofreduced pressure in said vessel into which said hydrocarbon in vaporousform is drawn; passing said rotating gas and said hydrocarbon vaporthrough a second zone of said vessel wherein the rotational speed ofsaid gas is gradually decreased and wherein said gas is gradually mixedwith said vapor causing a partial combustion of said hydrocarbon vapor;and passing said rotating gas and said hydrocarbon vapor into a thirdzone of said vessel wherein the reaction is completed.

3. Aprocess for the production of unsaturated hydrocarbons from liquidhydrocarbons which comprises: introducing a liquid hydrocarbon into acylindrical reaction vessel through a conduit having a free outlet inthe neighborhood of the inner wall of said vessel; introducing a gasselected from the group consisting of oxygen and oxygen-containing gasestangentially into said vessel ment of the vortex from the wall in afirst zone of said vessel, said rotating gas forming an axial region ofreduced pressure in said vessel; gradually vaporizing said hydrocarbonas said filrnlike band of liquid hydrocarbon moves through said vessel,whereby said hydrocarbon vapor is drawn into said axial region ofreduced pressure; passing said rotating gas and said hydrocarbon vaporinto a second zone of said vessel wherein the rotational speed of saidgas is gradually decreased and wherein said gas is gradually mixed withsaid vapor causing a partial combustion of said hydrocarbon vapor; andthereafter passing said rotating gas and said hydrocarbon vapor into athird Zone of said vessel wherein the reaction is completed.

4. A process as in claim 3 wherein said gas is introduced into saidvessel at a speed that is more than 80 meters per second faster than thespeed at which the said liquid hydrocarbon is introduced into saidvessel.

5. A process as in claim 3 wherein said gas is introduced into saidvessel at a speed that is from about 100 to about 200 meters per secondfaster than the speed at which the said liquid hydrocarbon is introducedinto said vessel.

References Cited in the file of this patent UNITED STATES PATENTS2,375,795 Krejci May 15, 1945 2,413,407 Dreyfus Dec. 31, 1946 2,750,420Hepp June 12, 1956 2,813,138 MacQueen Nov. 12, 1957 2,823,243 RobinsonFeb. 11, 1958

1. A PROCESS FOR THE PRODUCTION OF UNSATURATED HYDROCARBONS FROM LIQUIDHYDROCARBONS WHICH COMPRISES INTRODUCING A LIQUID HYDROCARBON THROUGH ACONDUIT HAVING A FREE OUTLET INTO A CYLINDRICAL REACTION VESSEL IN THENEIGHBORHOOD OF THE INNER WALL OF SAID VESSEL; INTRODUCING A GASSELECTED FROM THE GROUP CONSISTING OF OXYGEN AND OXYGEN-CONTAINING GASESTANGENTIALLY INTO SAID VESSEL THROUGH A SLOT NEAR THE POINT OFINTRODUCTION OF SAID LIQUID HYDROCARBON AND AT A SPEED GREATER THAN THESPEED OF SAID LIQUID HYDROCARBON, WHEREBY SAID HYDROCARBON FORMS AFILMLIKE BAND OF LIQUID ON SAID WALL; ROTATING SAID GAS ALONG THE WALLOF SAID VESSEL AT A SUFFICIENT SPEED TO PREVENT A DETACHMENT OF THEVORTEX FROM THE WALL, SAID ROTATING GAS FORMING AN AXIAL REGION OFREDUCED PRESSURE IN SAID VESSEL INTO WHICH SAID HYDROCARBON IN VAPOROUSFORM IS DRAWIN; PASSING SAID ROTATING GAS THROUGH A CONICAL MEMBERHAVING A CONE ANGLE OF LESS THAN 10*, THE ROTATIONAL SPEED OF SAID GASDECREASING AS IT PASSES THROUGH SAID CONICAL MEMBER, WHEREBY PROGRESSIVEPARTIAL COMBUSTION OF SAID HYDROCARBON TAKES PLACE; AND PASSING SAIDROTATING GAS AND SAID VAPOROUS HYDROCARBON INTO A SECOND CYLINDRICALMEMBER WHICH IS ADJACENT TO SAID CONICAL MEMBER, WHEREIN THE REACTION ISCOMPLETED.